In the semiconductor packaging industry, wire bonding continues to a primary method of providing electrical interconnection between two (or more) locations within a package. In a typical wire bonding application, a wire bonding tool (e.g., a capillary bonding tool in a ball bonding application, a wedge bonding tool in a wedge bonding application, etc.) is used to bond a first end of wire to a first bonding location to form a first bond. Then, a length of wire continuous with the first bond is extended toward a second bonding location. Then, a second bond (continuous with the first bond and the length of wire) is formed at the second bonding location. Thus, a wire loop is formed between the first bonding location and the second bonding location. During formation of wire bonds various types of energy (e.g., ultrasonic, thermosonic, thermocompressive, etc.) may be used, in connection with bond force and/or heat.
In certain types of semiconductor packages, various semiconductor dies are arranged in a “stacked die” configuration. In such packages, one or more of the dies may overhang other dies (or spacers, substrates, etc.). FIG. 1 illustrates such a package. In FIG. 1, a lower semiconductor die 102 is supported by a substrate 100 (where a wire loop 108 provides interconnection between a bonding location on die 102 and another bonding location on substrate 100). A spacer 104 is positioned between lower semiconductor die 102 and an upper semiconductor die 106. Upper semiconductor die 106 includes an unsupported portion that hangs over spacer 104 and lower semiconductor die 102. As such, upper semiconductor die 106 may be termed an “overhang die”.
In FIG. 1, it is desirable to form another wire loop between upper semiconductor die 106 and another location (e.g., substrate 100). FIG. 1 illustrates the beginning of the bonding process, as a ball bond 112 is being bonded (as a first bond) to a bonding location on upper semiconductor die 106 using a wire bonding tool 110 (where wire bonding tool 110 is carried by a bond head assembly 114). Because upper semiconductor die 106 is an overhang die, the die bends (i.e., die deflection, as shown in FIG. 1). This die deflection can result in damage to the overhang die itself (e.g., cracking, etc.) or damage through contact with other structures below the overhang die (e.g., such as wire loop 108).
Thus, it would be desirable to provide improved methods of controlling potential damage in connection with wire bonding in overhang die applications.